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Astron. Astrophys. 329, 329-338 (1998)

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1. Introduction

Since 1980, the solutions giving the position of the equator of the Earth cannot be computed with only a theory of the rigid Earth. The IAU 1980 adopted nutation series are deduced from the Kinoshita (1977) theory of the rotation of the rigid Earth, by convolution with the non-rigid Earth's transfer functions of Wahr (1981).

By using modern techniques like Very Long Baseline Interferometry (VLBI) precession and nutations may be presently observed with a precision of about 20 [FORMULA] as. The differences between the theory and the observation must reveal only the effects of the non-rigidity of the Earth, so it is necessary to build a theory of the rigid Earth with a precision better than 2 [FORMULA] as.

In Bretagnon et al. (1997) we have built analytical solutions for each of the Earth's three Euler angles [FORMULA], using truncated solution for the motion of the Moon. Over 1900-2050, the precision was 16 [FORMULA] as for [FORMULA], 8 [FORMULA] as for [FORMULA] and 15 [FORMULA] as for [FORMULA]. For improving our solution we have computed geocentric rectangular coordinates of the Moon referred to the ecliptic and equinox J2000 from the complete solution ELP 2000 (Chapront-Touzé, Chapront, 1983). Also we have computed the right-hand sides of the equations with a better accuracy.

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© European Southern Observatory (ESO) 1998

Online publication: November 24, 1997